In rigid magnetic media disk drives, the transducer, for writing and reading information on the media, typically is formed on or attached to a ceramic carrier, a "slider," which is supported by a flexible suspension, which is in turn mounted on an arm of an actuator assembly. The magnetic pole or poles of the transducer are positioned coplanar with the surface of the slider, which confronts the media. In the past, such sliders have been designed to "fly" above the surface of the rotating media at the minimum "flying height" consistent with the need to maintain sufficient separation in order to avoid catastrophic wear and achieve long term reliability. The need to fly low, in order to increase recording density and performance, is thus in conflict with constraints imposed by mechanical and interface considerations. The latter relate to a variety of design, manufacturing and quality control issues, not only of the slider but also of the surface properties of the media. In particular, tight tolerances are required in creating the "air bearing surface," configuring the "ramp," controlling "throat height" and "pole tip recession" and attaching the slider to the gimbal suspension structure. The allowable tolerances have decreased very rapidly, as the flying height has been reduced and recording density increased over the years, presenting greater and greater challenges to manufacture.
It should be noted, in passing, that similar considerations and limitations can be involved in the design and manufacture of all systems which utilize transducers to sense or record images from or to a medium. That is, the resolution of such systems is inversely related to the spacing separating the resolving elements of the transducer, e.g., an aperture in a near-field optical system, from the medium. As will become apparent, the present invention may be applicable to any system in which the particular geometry of a transmitting or receiving terminal of the transducer is important to signal transmission.
A particular manufacturing process that has been employed in defining critical features of transducers or heads used in magnetic read/write disk drive systems is the lapping of the transducers by an abrasive surface. With the typical heads of such systems that are designed to "fly" on an air layer during reading or writing operations with a disk, such lapping has been used to form the air bearing surfaces and ramps of sliders. A particular problem encountered in mass production of such heads is the differential extent to which a row of heads may be lapped, due to "bowing" of the row and other factors. In U.S. Pat. No. 5,321,882, Zarouri et al. propose that the lapping of a group of air bearing sliders is more advantageously accomplished by holding the sliders in a column rather than a row. On the other hand, Bischoff et al., in U.S. Pat. No. 5,117,589, disclose a device for adjusting the bowing of a row of sliders held by the device during lapping, by mechanically or electronically compensating for bowing.
Commonly, such lapping of flying heads includes an electrical lapping guide attached to or incorporated in the device holding the transducers in an attempt to determine when optimal material has been removed, for example, for the throat height of the heads. As noted in U.S. Pat. No. 4,675,986 to Yen, electrical lapping devices have a graded resistance at a surface of the holding device in order to measure the lapping of the heads by measuring the resistance of the holding device. U.S. Pat. No. 5,175,938 to Smith teaches means for improving the accuracy of an electrical lapping guide by combining different types of graded resistors. Similarly, in U.S. Pat. No. 4,914,868, Church et al. disclose a lapping control system for magnetoresitive transducers that measures the resistance of those transducers to determine lapping height. And Zammit teaches, in U.S. Pat. No. 5,065,483, a method for lapping thin film heads that compares a resistive lapping guide with a finished lapping guide in order to calculate appropriate lapping amounts of the heads.
Another approach to achieving smaller tolerances for head throat heights is to perform an additional step for adjusting throat heights after lapping. Amin et al., in U.S. Pat. No. 5,137,750, teach a method of making pole heads that may be etched after lapping to create contoured pole tips. U.S. Pat. No. 5,283,942 to Chen et al. similarly discloses an etching step which controls planarization of a gap layer at a pole tip. And in U.S. Pat. No. 5,327,638, Haines et al. teaches first lapping a magnetic core for a vertical recording head and then winding an electrical coil around the core.
Despite these advancements, a need for ever more accurate transducer dimensions calls for continued improvement in the processes used for their manufacture. Moreover, a dramatic recent departure from the conventional magnetic recording technology has resolved the conflicting demands between the reduction in flying height needed to increase data storage density and the increased tendency to crash as flying height is reduced. This conflict is resolved by adopting a fundamentally new slider/suspension design logic, which assumes at the outset the possibility of reliably operating the slider/transducer in continuous sliding contact, and is of key importance in U.S. Pat. No. 5,041,932 to Hamilton for INTEGRATED MAGNETIC READ/WRITE/FLEXURE/CONDUCTOR STRUCTURE, assigned to the assignee of the present invention. This new technology has demonstrated, in many hundreds of thousands of hours of cumulative testing, virtual freedom from "head crash" and the capability for reliable, long term operation of sliders in continuous sliding contact with the media. In consequence of these developments, the magnetic spacing loss has been reduced dramatically while the recording density has been correspondingly increased, and the manufacture of head/suspension structures has been greatly simplified.
It is with the preparation of a transducer surface for optimal conformation and operational confrontation with a media surface that the present invention is concerned. Therefore, it is a general objective of this invention to facilitate the manufacture of transducers so as to increase yield and operational performance and decrease costs. A specific objective of this invention is to provide simple, cost effective means and methods of preparing the media-confronting surface of sliding and flying heads in concert with their suspension structures, termed "sliders", so as to enable optimal magnetic interaction with the media.